A communication system can be seen as a facility that enables communication sessions between two or more entities such as user equipment and/or other nodes associated with the communication system. The communication may comprise, for example, communication of voice, data, multimedia and so on.
Communication systems providing wireless communication for user equipment are known. A cellular telecommunications system is a communication system that is based on use of radio access entities and/or wireless service areas. The access entities are typically referred to as cells. Examples of cellular telecommunications systems include standards such as the GSM (Global System for Mobile communications) or various GSM based systems (such as GPRS: General Packet Radio Service), AMPS (American Mobile Phone System), DAMPS (Digital AMPS), WCDMA (Wideband Code Division Multiple Access), TDMA/CDMA (Time Division Multiple Access/Code Division Multiple Access) in UMTS (Universal Mobile Telecommunications System), CDMA 2000, i-Phone and so on.
In a cellular system, a base transceiver station (BTS) provides a wireless communication facility that serves mobile stations (MS) or similar wireless user equipment (UE) via an air or radio interface within the coverage area of the cell. As the approximate size and the shape of the cell is known, it is possible to associate the cell to a geographical area. Each of the cells can be controlled by an appropriate controller apparatus.
Cellular systems typically support communication with user equipment changing locations (mobile users). The support for communications for mobile users may include support for handing existing connections from one cell to another cell. At least routing of calls or communications for a mobile user in a new cell is typically supported in cellular systems.
In a radio access network (RAN) based on a cellular system, communication takes place from the network to a mobile terminal or user equipment (UE) in downlink, and from the UE to the network in the up-link.
In certain communication systems, two types of transport channels—dedicated channels and common channels—may be provided. A common channel is a resource divided between all or a group of users in a cell, whereas a dedicated channel is by definition reserved for a single user.
An example of a common channel in a typical system is a random access channel (RACH). The RACH is mapped onto the Physical Random Access Channel (PRACH). It carries uplink common control information, i.e. Common Control Channel (CCCH), such as requests to set up radio resource control (RRC) connections. It may further carry dedicated control information, i.e. the Dedicated Control Channel (DCCH), between the UE and the network, established through the RRC connection setup procedure. The RACH is further used for sending dedicated user information, i.e. the Dedicated Traffic Channel (DTCH), such as small amounts of uplink packet data.
Thus during a RRC connection setup procedure, the RACH may be used by the mobile terminal in order to initiate access to the RAN. However, before the mobile terminal can send an RRC connection setup request to the RAN, it is typically required that the mobile terminal must have received and processed certain system information broadcast from the RAN. The system information is usually broadcast in blocks, each block grouping together system information elements of the same nature.
The system information may include a definition of what types of information the RAN requires from the mobile terminal in order to initiate a connection. In a cellular system, this information may relate, for example, to the relationship between the mobile terminal and different access entities of the communication system.
The information may enable the RAN to select the most appropriate access entity to serve the mobile terminal, to calculate the initial downlink power when transmitting to the mobile terminal and/or to select the active set when moving the terminal equipment into a different control state. For instance in a 3G WCDMA packet data mobile network, the terminal may be in one of a number of radio resource control states such as CELL_DCH (in which the terminal has a dedicated channel to the access network), CELL_FACH (Forward Access Channel, in which the terminal is tracked at cell level but shares an access channel with other terminals) and CELL_PCH (Paging Channel, in which the terminal is tracked at cell level and needs to be paged and shifted to a higher power control state before sending or receiving packet data). The cell reporting information may be required by the RAN in order to select the appropriate settings when shifting the mobile terminal to the active CELL_DCH state.
Thus the system may define that the mobile terminal needs to report the results of particular measurements to the RAN, the measurements relating to properties associated with signal transmission between the mobile terminal and the various access entities. After receiving the system information, the mobile terminal may send the required data (such as measurement results) to the RAN in a connection request message, according to the required reporting configuration specified in the system information.
A problem associated with this method is that the requirement for the mobile terminal to read certain system information before sending a connection request message can introduce a significant delay into the setup procedure, during which time the mobile terminal is unable to contact the RAN. A similar problem arises when the mobile terminal needs to send other types of message to the RAN (such as a measurement report message, a location update (e.g. cell update) or core network message) on a common transport channel such as RACH, before a dedicated physical channel between the mobile terminal and the RAN has been established.
One potential approach to solving this problem would be to allow the mobile terminal to send a connection request message or other message type on the common transport channel before it has read the system information. However, in this case it is not apparent how the required cell information should be provided from the mobile terminal to the RAN.